Gary Lewis Posted February 15, 2021 Author Share Posted February 15, 2021 But is a 512 ohm resistor enough to pull in a relay and power the alternator? If there is another ground path, will the light ever go out, as it does when the alternator starts charging and both sides of the filament come to the same potential? (Because they won't if there is a path to ground through the relay pull in) Guys - On the version with a warning light there won't be a relay. Just the light, with its resistor in parallel, going right to the alternator to bootstrap it in. That's the easy peasy one - that I haven't tackled yet. So, what am I missing? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 15, 2021 Share Posted February 15, 2021 Guys - On the version with a warning light there won't be a relay. Just the light, with its resistor in parallel, going right to the alternator to bootstrap it in. That's the easy peasy one - that I haven't tackled yet. So, what am I missing? Where's the voltmeter you want connected with a relay, to XYZ point of the charging system (cab/battery?) Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 15, 2021 Author Share Posted February 15, 2021 Where's the voltmeter you want connected with a relay, to XYZ point of the charging system (cab/battery?) In a Bullnose, up through 1985, you get either a warning light or an ammeter. Not both. We are converting the ammeter to a voltmeter so need a relay. But with a warning light there is no voltmeter so no need for a relay. Just use the wire from the light to bootstrap the alternator in, like was done on the 1G. Link to comment Share on other sites More sharing options...
JimsRebel Posted February 15, 2021 Share Posted February 15, 2021 And speaking of the LG/R wire, the relay will be pulled in by it rather than stator voltage. That's because it seems easier to wire it up that way since you can use the LG/R wire both to pull the relay in as well as to provide power to the voltmeter. Snip.... If you use the LG/R wire to power the volt meter you do not need a relay. The voltmeter would only get power with the Key ON. It is my understanding that you added a relay, when the voltmeter was reading "always HOT power" near the battery, to eliminate the parasitic battery drain ( .068 amps). Using a relay with a idiot light would cause a constant current flow through the light bulb filament, and a series circuit. You should test this on the bench with a relay - light combination. Or maybe the ALT would source the needed current for the relay. This is not something I would not recommend, at least at this point, to many unknowns. Regarding the 2G harness photo, showing the cut points: Keep in mind you will have to replace the voltage regulator plug with a NEW plug that has all 3 wires. Jim #2 Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 15, 2021 Author Share Posted February 15, 2021 And speaking of the LG/R wire, the relay will be pulled in by it rather than stator voltage. That's because it seems easier to wire it up that way since you can use the LG/R wire both to pull the relay in as well as to provide power to the voltmeter. Snip.... If you use the LG/R wire to power the volt meter you do not need a relay. The voltmeter would only get power with the Key ON. It is my understanding that you added a relay, when the voltmeter was reading "always HOT power" near the battery, to eliminate the parasitic battery drain ( .068 amps). Using a relay with a idiot light would cause a constant current flow through the light bulb filament, and a series circuit. You should test this on the bench with a relay - light combination. Or maybe the ALT would source the needed current for the relay. This is not something I would not recommend, at least at this point, to many unknowns. Regarding the 2G harness photo, showing the cut points: Keep in mind you will have to replace the voltage regulator plug with a NEW plug that has all 3 wires. Jim #2 Jim - In reverse order: When you say "you will have to replace the voltage regulator plug with a NEW plug that has all 3 wires" do you mean a new 3G plug? As I said above, I don't see a need for a relay when there's a warning light. There is no voltmeter and we added the relay for the voltmeter. And you are exactly right, the relay is to eliminate the constant drain of the voltmeter when the engine is off. As for the LG/R, you are right that you can use it to power the voltmeter w/o a relay. Which is why I've shown it that way on the Monitoring At The Ignition Switch tab under 2G. (I want to get the 2G tab done before moving on to the 1G tab.) Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 15, 2021 Share Posted February 15, 2021 Jim - In reverse order: When you say "you will have to replace the voltage regulator plug with a NEW plug that has all 3 wires" do you mean a new 3G plug? As I said above, I don't see a need for a relay when there's a warning light. There is no voltmeter and we added the relay for the voltmeter. And you are exactly right, the relay is to eliminate the constant drain of the voltmeter when the engine is off. As for the LG/R, you are right that you can use it to power the voltmeter w/o a relay. Which is why I've shown it that way on the Monitoring At The Ignition Switch tab under 2G. (I want to get the 2G tab done before moving on to the 1G tab.) My 2G had a three wire regulator plug. Maybe some didn't??? Link to comment Share on other sites More sharing options...
JimsRebel Posted February 15, 2021 Share Posted February 15, 2021 Jim - In reverse order: When you say "you will have to replace the voltage regulator plug with a NEW plug that has all 3 wires" do you mean a new 3G plug? As I said above, I don't see a need for a relay when there's a warning light. There is no voltmeter and we added the relay for the voltmeter. And you are exactly right, the relay is to eliminate the constant drain of the voltmeter when the engine is off. As for the LG/R, you are right that you can use it to power the voltmeter w/o a relay. Which is why I've shown it that way on the Monitoring At The Ignition Switch tab under 2G. (I want to get the 2G tab done before moving on to the 1G tab.) I did see the drawing, and yes it was correct, but the text earlier stated the relay would be used with the LG/R wire. Quote... My 2G had a three wire regulator plug. Maybe some didn't??? The drawing used here only has 2 wires. My truck only had 2 wires. It might just be a 1986 only issue, I don't know. On a 1986, with a 2G ALT, if it fails and you pick up a replacement 2G at the auto parts store, it will NOT work if you only have 2 wires on your wire regulator plug. You will have to replace the plug with a 3 wire plug to get it to work. Replacement voltage regulator plugs are sold as 2G - 4G. If you had a 3 wire 2G voltage regulator plug, it would fit (and work fine) into the 3G ALT as is. Jim #2 Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 15, 2021 Share Posted February 15, 2021 I did see the drawing, and yes it was correct, but the text earlier stated the relay would be used with the LG/R wire. Quote... My 2G had a three wire regulator plug. Maybe some didn't??? The drawing used here only has 2 wires. My truck only had 2 wires. It might just be a 1986 only issue, I don't know. On a 1986, with a 2G ALT, if it fails and you pick up a replacement 2G at the auto parts store, it will NOT work if you only have 2 wires on your wire regulator plug. You will have to replace the plug with a 3 wire plug to get it to work. Replacement voltage regulator plugs are sold as 2G - 4G. If you had a 3 wire 2G voltage regulator plug, it would fit (and work fine) into the 3G ALT as is. Jim #2 Yep, mine did. But maybe that's something that changed with Bricknose? I can't say. I only know what I encountered. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 15, 2021 Author Share Posted February 15, 2021 I did see the drawing, and yes it was correct, but the text earlier stated the relay would be used with the LG/R wire. Quote... My 2G had a three wire regulator plug. Maybe some didn't??? The drawing used here only has 2 wires. My truck only had 2 wires. It might just be a 1986 only issue, I don't know. On a 1986, with a 2G ALT, if it fails and you pick up a replacement 2G at the auto parts store, it will NOT work if you only have 2 wires on your wire regulator plug. You will have to replace the plug with a 3 wire plug to get it to work. Replacement voltage regulator plugs are sold as 2G - 4G. If you had a 3 wire 2G voltage regulator plug, it would fit (and work fine) into the 3G ALT as is. Jim #2 Ok, I think I see what is being said about the 2G regulator plug. But we addressed the needed 3G harness on the tab at Wiring It/3G Harness. So we've effectively said you need a new regulator plug. However, your point is that if you have a 2G regulator plug with 3 wires you can use it on a 3G. Right? If so, I could say that in the discussion about the regulator plug. As for the relay being used with the LG/R wire, it is - in the situation where you want to monitor battery voltage. Here's the way I understand how we are using that wire: Warning Light: LG/R wire goes directly to I terminal on the regulator Voltmeter Reading Ignition Switch Voltage: LG/R wire goes both to the I terminal as well as to the positive side of the voltmeter Voltmeter Reading Battery Voltage: LG/R wire goes to both the I terminal as well as is used to pull in the relay. But, note that the way I had the relay wired was W.R.O.N.G! I've corrected it now, but previously I was setting the voltmeter up to read the difference between the battery voltage and the ignition switch voltage. Anyway, I've now changed the wires to red and wrapped the sense wire, the one going to the A terminal on the regulator, back to the alternator's output, as we've discussed. And, fixed the error in the relay wiring. With that I believe the 2G wiring when monitoring at the battery is both correct and done. Please check it out. Link to comment Share on other sites More sharing options...
Machspeed Posted February 15, 2021 Share Posted February 15, 2021 Ok, I think I see what is being said about the 2G regulator plug. But we addressed the needed 3G harness on the tab at Wiring It/3G Harness. So we've effectively said you need a new regulator plug. However, your point is that if you have a 2G regulator plug with 3 wires you can use it on a 3G. Right? If so, I could say that in the discussion about the regulator plug. As for the relay being used with the LG/R wire, it is - in the situation where you want to monitor battery voltage. Here's the way I understand how we are using that wire: Warning Light: LG/R wire goes directly to I terminal on the regulator Voltmeter Reading Ignition Switch Voltage: LG/R wire goes both to the I terminal as well as to the positive side of the voltmeter Voltmeter Reading Battery Voltage: LG/R wire goes to both the I terminal as well as is used to pull in the relay. But, note that the way I had the relay wired was W.R.O.N.G! I've corrected it now, but previously I was setting the voltmeter up to read the difference between the battery voltage and the ignition switch voltage. Anyway, I've now changed the wires to red and wrapped the sense wire, the one going to the A terminal on the regulator, back to the alternator's output, as we've discussed. And, fixed the error in the relay wiring. With that I believe the 2G wiring when monitoring at the battery is both correct and done. Please check it out. I'll let the two Jim's respond. We need an "eating popcorn" emoji, cause that about all I'm doing on this ride. Link to comment Share on other sites More sharing options...
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